Combustion chambers for pistons



March 21, 1961 s. MEURER COMBUSTION CHAMBERS FOR PISTONS Filed June 9.1958 zzyz 4 Sheets-Sheet 1 INVENTOR ATTORN 6' March 21, 1961 4Sheets-Sheet 2 Filed June 9, 1958 INVENTOR March 21, 1961 Filed June 9,1958 s. MEURER 2,

COMBUSTION CHAMBERS FOR PISTONS 4 Sheets-Sheet 3 f u I INVENTOR March21, 1961 s. MEURER 2,975,773

COMBUSTION CHAMBERS FOR PISTONS Filed June 9, 1958 4 Sheets-Sheet 4INVENTOR ATT RNEY 7 an area of the chamber wall.

r tes United COMBUSTION CHAMBERS FOR PISTONS Siegfried Meurer, Numberg,Germany, assignor to Maschinenfabrik Augsburg-Numberg A.G., Nurnberg,Germany This invention relates to combustion chambers for pistons. Inparticular, the invention is directed to combustion chambers forself-ignition engines.

The piston of this invention is designed to operate in self-ignitionengines such as disclosed in US. patent to Meurer et al. No. 2,907,308.In such engine, the liquid fuel is injected into a hollowcombustionchamber in the piston. the major portion of the fuel travels over ashort free path and is applied immediately to the wall of the combustionchamber. After striking the chamber wall, the fuel spreads out as a filmover a part of the wall. The remaining minor portion of the fuel isatomized directly in the air in the chamber and is self-ignited forigniting the fuel vaporized from the film of fuel. Combustion air isswirled over the film of fuel to vaporize the same.

In these engines, it is desirable to have the fuel cover as much aspossible of the chamber wall. If the chamber, as in former pistons, isspherical or ellipsoidal and the fuel' strikes the wall at a sharpangle, the fuel is spread as a film in a satisfactory manner. Because ofthe kinetic energy of the fuel, it has a tendency to spread peripherallyabout the wall of the combustion chamber. However, in these chambers,the spreading of the fuel is handicapped by the concave curve of thespherical or ellipsoidal chamber. Such chamber forms act in the natureof a groove with the fuel tending to flow along the bottom thereof andnot completely spread out.

The object of this invention is to produce a combustion chamber formedas a body of rotation and having a shape such that the fuel will spreadout evenly in all directions on the wall of the chamber.

'One way of accomplishing the object of the invention is to form thecombustion chamber wall at least in the area adjacent the places wherethe fuel jet strikes the wall as a flat or convexly curved surfaceextending inthe direction of the longitudinal axis of the piston andchamber. 'In other words, the chamber wall is fiat or con ,vexly curvedperpendicularly to the circumferential direction of the body ofrotation, at least in the areas where the fuel strikes the chamber wall.

By so constructing the combustion chamber, the undesirable groovedeffect described above is avoided, and the fuel is spread as a film overas large as possible Because of the kinetic energy of the fuel, it stilltends to spread circumferentially about the wall of the chamber, butsimultaneously also has the tendency to spread in other directions.

In another form of the invention, the flat or convexly curved surfaceextending in the direction of the longitudinal axis of the piston can becontinued into a concave portion adjacent the opening of the combustionchamber through the head of the piston. In such construction, aconstricted opening is formed which enhances the air swirl produced inthe chamber.

In another form of the invention, the combustion chamber is in the formof a hollow cone. This form is used especially when the combustionchamber is to have a The injection is made in such a way that atentPatented Mar. 21, 1961 hollow conical section forming the side wall ofthe charm her and the bottom is shaped as a torus. A further form ofchamber is in having two oppositely directed conical chamber portions,with the two portions connected at their bases. A chamber so constructedhas been found to improve the cold stanting of an engine. This isbecause of the sudden change given the direction of the spreading fuelover the joint between the two conical sections.

. The fuel at this point is momentarily detached from the wall.Consequently, the air swirling across this separated fuel atomizes thefuel which is of special advantage for high boiling point fuels. Asimilar effect can be obtained if the chamber wall and bottom are ofspherical shapes with diflerent curvatures. In the latter construction,as compared to the two conical portion construction, the momentaryseparation of the fuel from the film can be accomplished closer to theopening into the combustion chamber so that the atomization is moreeffective in the starting of the engine.

When the combustion chamber is in the form of two conical portions,these conical portions can be symmetrical and axially aligned. However,in a modified construction, the conical portions can be eithernonaxially aligned, or can be axially out of line, or can benon-symmetricalfor purposes of forming fuel films desirable for certaincombustion processes. a

A still further form of the invention has the combus tion chamberopening connected to the combustion chamber by a short cylindrical neck.A variation of this is to form the neck as a polygon, and especially asa triangle. The fuel can be injected from one corner of the triangle.Also,-when the neck is triangular and two valves are provided for thecylinder, the fuel injection can be through one corner while the othertwo corners of the triangle are positioned beneath the valves. In astill further modified form, the neck can be elliptical, and then thefuel nozzle is positioned so that its longitudinal axis is aligned withthe major axis of the el liptical neck.

A periodical momentary separation of the fuel from the film on thecombustion chamber wall, which in connection with the forming ofsecondary swirls to atomize the fuel, can also be obtained by other waysof joining the conical combustion chamber portions. As alreadymentioned, Spherical portions of different curvature can be used.Basically, the atomizing effect can be obtained if the combustionchamber wall has an irregularity. For producing such an irregularity,another form of the invention has a stepped wall surface, with the stepsextending transversely to the direction of both the injected fuel andthe air swirl in the chamber.

The means by which the objects of the invention are obtained aredescribed more fully with reference to the. accompanying drawings, inwhich:

Figure 1 is a longitudinal cross-sectional view through a piston ina'cylinder with the piston having a combustion chamber according to oneform of the invention;

Figures 2, 3 and 4, respectively, are modified forms of the combustionchamber;

Figure ,5 is a top plan view of a piston having an elliptical opening inthe combustion chamber;

Figure 6 is a transverse sectional view through a piston 7 having astepped combustion chamber wall;

Figure 7 is a longitudinal view through a piston constructed accordingto Figure 6;

Figures 8, 9 and 10 are cross-sectional views similar to Figure 1 butshowing, respectively, further modified forms of the combustion chamber;

Figure 11 is a plan view of a piston having a cylindrical neck formingthe opening into the combustion chamber;

Figures 12 and 13 are modifications of the neck opening and show,respectively, a triangular and a hexagonal opening; and

Figure 14 is a cross-sectional view showing a still further modificationof the invention shown in Figure 1.

As Shown in Figure 1, the combustion chamber 1 having the shape of abody of rotation is positioned in the piston head of piston 2, thechamber being coaxial with the axis of piston 2 and cylinder 3. A nozzle4 is inclined in the cylinder head 4a above the combustion chamber. Themajor portion of the injected fuel is applied to the combustion chamberwall by several fuel jets 4b which are directed at a sharp angle towardthe wall and form a film thereon. This film is vaporized from the walland mixed with the air swirling in the chamber to produce a combustiblefuel air mixture. The minor portion of the fuel is atomized immediatelyin the air swirling in the chamber. This atomizing is accomplished byeither deflecting a part of the injected fuel into the air or by aspecial ignition jet, not shown. As the fuel leaves the nozzle, it has akinetic energy which moves the fuel circumferentially around and uponthe combustion chamber wall. In a vertical direction, as shown in Figure1, and in the direction of the longitudinal axis of the piston, thespreading of the fuel is enhanced by a convexly curved portion of thechamber wall, this curved portion extending between the planes 55 and6-6. A concave portion forms the bottom 7 of the combustion chamber,which bottom is joined to the convexly curved portion. At the top of thechamher is a concave portion 8 which extends from the convexly curvedportion to the cylindrical neck 9 through which the combustion chambercommunicates with the piston cylinder through the piston head, andthrough which the fuel is injected into the cylinder. Concave portionand neck 9 form a kind of a restriction of the upper end of thecombustion chamber which produces a better swirling of the air Withinthe chamber. As shown in Figure 8, if neck 9 is omitted, the combustionchamber wall is extended by the continued outwardly curved portion 10.In horizontal cross-section, the combustion chamber can be in the shapeof a circle or an ellipse.

In Figure 2, the combustion chamber is in the form of a cone. Again,chamber 1 is coaxial with piston 2 and cylinder 3, and opens through thepiston head. The side wall 11 of chamber 1 is connected by a curvedportion with the fiat bottom 13. The inclination of wall 11 can bereversed, and it has been found that the diameter 14 should preferablybe from about 0.8 to 1.4 times the diameter 15 of the opening throughthe piston head. To enhance the spreading of the fuel in the directionof the longitudinal axis of the chamber, side wall 11 is so formed as toappear as a straight line in the cross-sectional view of Figure 2.However, side wall 11 can be convexly curved as shown in Figure l toenhance further the spreading of the fuel over a large surface of thechamber wall. In horizontal cross-section, the combustion chamber canappear as circular, elliptical or polygonal.

In Figure 3, the chamber 1 differs from that shown in Figure 2 by theshape of the chamber bottom. While in Figure 2, bottom 13 is flat, inFigure 3 the bottom 13a between curved portions 12 is in the shape of acone with the apex thereof pointing to the interior of chamher 1. Thusthe combustion chamber has a conical side wall 11 and a bottom in theform of a toms.

Figure 4 has a chamber 1 composed of two oppositely directed conicalportions with their bases joined on the line 16. Here also the chamber 1is coaxial with the longitudinal axis of the piston. Along the line 16,the Wall of the chamber is interrupted to form an irregular surfacewhich causes the fuel film being applied to be momentarily separatedfrom the chamber wall. This separated fuel mixes with the air swirl inthe chamber and thus causes an atomizingof at least a part of thisseparated fuel.

When it is desired to apply the fuel to particular wall areas, such canbe accomplished by the arrangement of the portions of the chamber wall.For example, the conical sections, instead of being coaxial, can bedisplaced with respect to one another as by having the two axes at anangle to each other, as in Figure 9, or by making the conical sectionsunsymmetrical with respect to each other, as in Figure 10. Combinationsof the above are also possible.

The momentary separation of the film being applied to the wall, asdisclosed in Figures 4, 9 and 10, can be further increased if step-likeprojections 17 are formed in the wall, as shown in Figures 6 and 7.These steps form an irregular wall surface with the separation of thefuel film occurring at the interruptions. The fuel spreading along thechamber wall is intercepted by the air swirl during the time it passesstep 17 and then contacts the chamber wall. The secondary air swirlsformed at these steps mixes with the fuel separated from the wall toatomize the fuel, which is very desirable with fuels having a highboiling point. Nozzle 4, through which the fuel is injected into chamber1, is preferably mounted close to one of the steps 17. Fuel jets 4a havethe direction of nozzle 4. Steps 17 are directed either parallel to orat an angle to the axis of chamber 1 and trans versely of the directionof the fuel jets and the direction of the air swirl.

The opening of the combustion chamber 1 through the piston head can beas heretofore stated by means of a neck 9. As shown in Figure 1, thiscan be a cylindrical neck. In Figures 5, ll, 12 and 13, the cylindricalopening is replaced by either a polygon 9a, Figure 13, or a circle 9d,Figure 11. If the opening is an equilateral triangle 9b, as in Figure12, the fuel is injected from a nozzle 4 located in one corner of thetriangle. When two valves 19 and 20, Figure 12, are provided for thecylinder, each of these valves is positioned over one of the other twocorners of the triangle 9b. As shown in Figure 5, the opening 9c iselliptical with the major axis of the ellipse being aligned with thelongitudinal axis of the nozzle 4.

In Figure 14, nozzle 4, instead of extending through a neck, ispositioned to inject fuel through an auxiliary bore 21. This bore 21 aswell as the neck 9' are inclined with respect to the longitudinal axisof the chamber.

Having now described the means by which the objects of the invention areobtained, I claim:

1. In a piston having a combustion chamber for receiving a film of fuelinjected upon the wall of the chamber, said fuel being then vaporizedand burned, the improvement comprising a downwardly directed generallyconically shaped combustion chamber extending from the top surface ofthe piston into the piston body, said chamber having a convexly curvedwall portion extending entirely around the longitudinal axis of saidchamber for receiving and spreading said film of fuel.

2. In a piston as in claim 1,- further comprising a cylindrical neckportion forming an opening from said chamber to the surface of thepiston head.

3. In a piston as in claim 1, further comprising a polygonal neckportion forming an opening from said chamber to the surface of thepiston head.

4. In a piston as in claim 3, said neck portion being triangular andadapted to have fuel injected through one corner thereof,

5. In a piston as in claim 4, said triangular neckportion having itssecond and third corners positioned at the valve openings into a pistoncylinder.

- 6. In a piston as in claim 1, further comprising an elliptical neckportion forming an opening from said chamberto the surface of the pistonhead.

7. In a piston as in claim 6, said elliptical neck portion having itsmajor axis adapted to be aligned with the axis of a fuel nozzle.

8. In a piston as in claim 1, said combustion chamber having a concavewall portion and lying between the surface of said piston and saidconcave portion.

9. In a piston as in claim 1, said convexly curved wall portion beinginclined downwardly from the upper edge of the chamber opening in thepiston surface and joined to a concave bottom wall.

10. In a piston as in claim 1, further comprising a neck between saidtop surface of said piston and said convexly curved wall portion, saidneck being parallel to the longitudinal axis of said piston.

11. In a piston as in claim 10, said neck forming a triangular openingin the top surface of said piston.

12. In an internal combustion engine having a cylinder and a piston,means for introducing air into said cylinder and simultaneouslyimparting to such air a swirling mo tion about the cylinder axis, saidpiston having a combustion chamber of smaller diameter than the cylinderand communicating therewith through a generally centrally locatedopening whereby the swirling air, when compressed, will be introducedinto the combustion chhmber with an accelerated velocity of swirl, andmeans including an injection nozzle for injecting liquid fuel into saidcombustion chamber with said nozzle being oriented to atomize a minorportion of the fuel in said combustion chamber and to direct the majorportion of the fuel in the direction of the air swirled through saidopening and onto said wall portion, the improvement comprising agenerally conically shaped combustion chamber having a convex wallportion extending entirely around the longitudinal axis of said chamberfor receiving said major portion of said fuel.

13. In an. internal combustion engine as in claim 12, said opening beingtriangularly shaped.

14. In an internal combustion engine as in claim 13, said nozzle beingoriented through a first corner of the triangular opening.

15. In an internal combustion engine as in claim 14, further comprisingan intake and an exhaust valve for said cylinder with each valve beinglocated, respectively, at a second and a third corner of said opening.

16. In an internal combustion engine as in claim 12, said opening beingelliptically shaped.

l7.' In an internal combustion engine as in claim 16, said nozzle beingaligned with the major axis of said elliptically shaped opening.

References Cited in the file of this patent UNITED STATES PATENTS2,622,570 Nallinger Dec. 23, 1952 2,718,882 Gerecke Sept. 27, 19552,803,229 Schwaiger Aug. 20, 1957 2,887,995 Stump May 26, 1959 FOREIGNPATENTS 643,351 Great Britain Sept. 20, 1950 789,423 Great Britain Jan.22, 1958 1,067,634 France Jan. 27, 1954 1,078,961 France May 19, 1954

